History

Fractures or luxations should be suspected if a loud crack is heard, there is acute non-weight bearing lameness, the limb is misaligned, or the limb is visibly unstable.

Physical examination

Physical examination of the injured horse should be completed in the best possible setting to avoid further injury to the horse, or to bystanders. Help should be obtained to facilitate crowd control. A knowledgeable handler should be identified to help with horse restraint. While the veterinarian is examining the horse, the person responsible for making decisions on the patient should be sought, and emergency transportation (ideally, an equine ambulance) should be organized.

If the horse is recumbent, examination should be completed before attempting to stand the horse. If the horse is standing, examination should be completed before attempting to move the horse. Sedation and a twitch can be used to help restraint. For sedation, an alpha₂ agonist such as xylazine, or xylazine and acepromazine can be used. If sedation is needed immediately after maximal exercise, up to double the standard dosage regimen may be required to achieve effective sedation.¹ Butorphanol or detomidine should be reserved for horses that are not controlled with xylazine. It is important to remember that alpha₂ agonists will often cause the horse to lean forward, which may increase the weight on an injured forelimb and decrease the ability to manipulate the limb. Therefore the minimal effective dose should be used. In addition, heavy sedation will prolong the exercise-induced increase in body temperature, which may be significant in a hot humid environment. Active cooling by washing with cold water is an effective method of facilitating heat dissipation.² If the horse is recumbent and there is concern for a serious injury, general anesthesia should be induced and maintained until further assessment is made. General anesthesia can be safely induced in horses following maximal exercise using sedation with a combination of xylazine and acepromazine, followed by induction of anesthesia with ketamine and diazepam or tiletamine–zolazepam. The combination of guaifenesin and thiopental produces more hypotension and is less desirable.³

Once restraint is achieved, a brief assessment of circulatory status should be made, by evaluating heart rate, mucous membrane color, capillary refill time, and pulse quality. Identification of a heart rate of greater than 80 beats per minute accompanied by a delayed capillary refill time and poor peripheral pulse quality indicates the need for intravenous fluid support.

Once the general status of the patient has been assessed, location and assessment of the injury follows. It is useful to divide the limbs into four levels, which will help define the method of coaptation (Fig. 58.1).⁴ Note that flexor tendon injuries located at the level of the metacarpus/metatarsus are considered level 1 injuries.

The presence of a fracture can be determined by: instability, crepitus, or abnormal motion. Luxations can be suspected when there is abnormal lateral-to-medial motion at the level of a joint, and can be confirmed with stress radiographs.

Special examination

Radiographic examination is indicated to confirm the presence of a fracture or luxation. If radiographic equipment is unavailable on site, external coaptation should be applied as if a fracture or luxation exists and the horse transported to a referral facility for further examination.

It is important to also remember that incomplete (hairline) fractures of the radius, tibia and other bones can be difficult to demonstrate radiographically, particularly in field conditions. Therefore, in the presence of severe lameness with pain localized to a long bone, external coaptation should be completed before transportation, to avoid catastrophic displacement of a fracture.

Laboratory examination

Laboratory determinations of biochemistry profile indices are more commonly available even in field situations. If available, parameters of hydration and electrolyte balance are useful to dictate fluid volume and type. In particular, measurement of lactate concentration using point-of-care equipment can provide a good evaluation of perfusion.⁵

Therapeutic aims

Therapy

The principles of emergency coaptation include:

Bandage and splint application

Any wound should be carefully cleaned and debrided. An antiseptic ointment can be applied and held in place with conforming gauze. Cotton padding is applied to the entire length of the segment to be immobilized, and held in place with gauze followed by non-stretch bandage material. The bandage should be snug, to avoid loosening with packing of the cotton material. The splints are then applied and held in place, ideally with fiberglass casting tape. Whenever using casting tape, at least six layers should be applied. Casting tape is particularly useful if there is a luxation, as these can be difficult to keep stabilized. If unavailable, heavy tape can be used. It is important to make sure the splints are well padded to avoid the development of sores. See Box 58.1.

Immobilization of level 1 injuries

Level 1 injuries include phalangeal fractures, fetlock, pastern or coffin joint luxations, and severance of one or more flexor tendons. Although technically a level 1 injury, extensor tendon lacerations require a different mode of splint application and will be presented separately. Forelimb and hindlimb immobilization differ slightly, because of the presence of the reciprocal apparatus in the hindlimb.

Forelimb

In forelimb injuries, immobilization is best accomplished by aligning the cannon bone with the phalanges, to establish a straight column (Fig. 58.2). The horse will bear weight on its toe. To accomplish this goal, the forelimb is held above the carpus, bandaged, and the splint is applied on the cranial aspect of the distal limb, extending from the toe to the carpus. If there is latero-medial instability, a lateral splint can also be applied. Alternatively, the splint can be held in place using casting tape.

Hindlimb

In the hindlimb, the reciprocal apparatus prevents extension of the distal limb if the animal is non-weight bearing. Therefore the limb is best immobilized by applying the splint on the caudal aspect of the limb, from the toe to the point of the hock (Fig. 58.3). Again, if there is latero-medial instability, a lateral splint should also be placed or casting used to immobilize the splint. A cranial splint can also be placed; however, to facilitate placement, the limb can be pulled forward to straighten the fetlock.

Use of the Kimzey^a apparatus

A commercially available splint is available for level 1 injuries (Fig. 58.4). The advantages of this splint are that it is readily available, easy to apply and is effective in achieving immobilization. Two configurations are available: one with a slightly forward angled bar (for the forelimb) and one with a backward angle with the curve at the level of the fetlock (for the hindlimb). In the author’s experience, the forward angle configuration is more effective for either fore- or hindlimb injuries. When used for prolonged immobilization, the stall should be deeply bedded to improve support of the foot. Alternatively, a heel piece can be welded onto the splint to increase weight-bearing surface area. Non-slip tape should be placed on the foot plate to make it less slippery, particularly on cement floors.

Immobilization of level 2 injuries

Examples of level 2 injuries include cannon bone fractures, wounds of the carpus or hock, olecranon fractures and radial nerve paralysis. Forelimb and hindlimb immobilization will again be discussed separately, because the angle of the hock requires a different splint configuration.

Forelimb

In level 2 injuries, two splints are needed, applied at 90-degree angle, with one splint lateral and one splint caudal. The splints need to extend from the hoof to the elbow (Fig. 58.5). For olecranon fractures and radial nerve paralysis, the goal of immobilization is to prevent tendon contracture and injury to the dorsal aspect of the limb. Only a caudal splint is needed for these types of injuries.

Hindlimb

As in the forelimb, two splints are needed, one applied laterally and the other applied caudally, from the hoof to the stifle. The angle of the hock makes it difficult to apply a caudal splint. Therefore the caudal splint can end at the point of the hock, rather than at the stifle (Fig. 58.6). Alternatively, if possible, a splint can be molded to the hock so it can be applied.

Immobilization of level 3 injuries

Level 3 injuries include fractures of the radius or tibia. With fractures at this level, the flexor muscles become abductors, resulting in displacement and comminution of the medial aspect of the limb. The medial aspect of both the radius and ulna does not include a muscle mass to help prevent penetration of the skin by fractured bone. Therefore the goal of external coaptation is to prevent abduction of the limb.

Forelimb

The splint is applied to the lateral aspect of the limb, and must extend from the hoof to the withers (Fig. 58.7). The tip of the splint can be taped around the chest for further stability.

Hindlimb

The splint is applied to the lateral aspect of the limb, extending from the hoof to the hip (Fig. 58.8).

Immobilization of level 4 injuries

Level 4 injuries include fractures of the scapula, humerus, femur or pelvis. External coaptation is not recommended for these injuries as these areas are not amenable to bandaging. Reliance on the hematoma and swelling around the injury for immobilization is needed. An immobilizing bandage should not be applied to the distal limb, as it will make it more awkward to move, and may increase motion at the fracture site. Increased motion at the fracture in return can result in severance of major vessels and significant and potentially fatal hemorrhage. If a fractured pelvis is present, the need for transportation should be discussed, as moving of the fracture segments can result in lacerations of major vessels. General anesthesia for pelvic fracture should be delayed for three to four weeks, to avoid fatal hemorrhage.